WO2021013848A1

WO2021013848A1 - Continuous hydroformylation process with catalyst substitution

Info

Publication number: WO2021013848A1
Application number: PCT/EP2020/070581
Authority: WO
Inventors: Alexander HENSEL; Ruben Fernandez Diaz; Wolfgang Greb; Jörg Botterhuis; Gregor MEIER
Original assignee: Oq Chemicals Gmbh
Priority date: 2019-07-24
Filing date: 2020-07-21
Publication date: 2021-01-28
Also published as: EP3770144B1; EP3770144A1; US20220371979A1; KR20220038139A; JP7335417B2; JP2022540887A

Abstract

The present invention relates to a continuous two-phase hydroformylation process for producing aldehydes from olefins by means of carbon monoxide, hydrogen and a transition metal catalyst in a reaction zone, the transition metal being in the form of a water-soluble catalyst complex, the process comprising the following steps once or several times: a) carrying out hydroformylation by reacting the olefins, carbon monoxide and hydrogen on a water-soluble transition metal catalyst having water-soluble organophosphorus ligands in the reaction zone; b) reducing the concentration of the olefins in the reaction zone by reducing the olefin supply to the reaction zone and removing at least part of the catalyst solution from the reaction system, it being possible to carry out the sub-steps of removing catalyst solution and of reducing the olefin concentration simultaneously or successively in this order or in reverse order; c) supplying a solvent, a transition metal source and water-soluble organophosphorus ligands to the reaction system, it being possible to supply the components simultaneously or successively in any order; d) increasing the concentration of the olefins in the reaction zone by increasing the olefin supply to the reaction zone and carrying out hydroformylation by reacting the olefins with carbon monoxide and hydrogen.

Description

Continuous hydroformylation process with catalyst substitution

The present invention relates to a continuous two-phase

Hydroformylation process for the preparation of aldehydes from olefins by means of

Carbon monoxide, hydrogen and a transition metal catalyst in a reaction zone, the transition metal being in the form of a water-soluble catalyst complex, the process comprising the following steps one or more times:

a) Hydroformylation by reacting the olefins, carbon monoxide and hydrogen on a water-soluble transition metal catalyst comprising water-soluble ones

Organophosphorus ligands in the reaction zone;

b) reducing the concentration of olefins in the reaction zone by reducing the olefin feed to the reaction zone and removing at least a portion of the

Catalyst solution from the reaction system, the partial steps of catalyst solution removal and the reduction in the olefin concentration being able to take place in this or the reverse order, simultaneously or in succession;

c) adding a solvent, a transition metal source and water soluble

Organophosphorus ligands to the reaction system, it being possible for the components to be added simultaneously or one after the other in any order;

d) increasing the concentration of the olefins in the reaction zone by increasing the olefin feed to the reaction zone and hydroformylating by reacting the olefins with carbon monoxide and hydrogen.

Hydroformylation processes have long been known in a wide variety of processes. What they all have in common is that olefins are converted to aldehydes in the presence of hydroformylation catalysts with hydrogen and carbon monoxide, the latter usually fed to the reaction as synthesis gas. So l for example the hydroformylation of propylene a mixture of straight-chain n- and branched i-butyraldehyde, of which the n-isomer is usually the economically desired product.

While the reactions were initially carried out over cobalt catalysts, rhodium has now established itself as advantageous. In comparison to cobalt catalysis, high productivities and preferred n / i ratios can be obtained by means of rhodium complex catalysts under comparatively milder reaction conditions. In addition, through the choice of suitable ligands, the solubility properties of the catalyst can be set within certain limits, which makes it easier to recover the expensive catalyst and also influences the catalytic properties of the rhodium-ligand complex.

Due to the flexibility of the implementation have been catalyzed for rhodium

In principle, hydroformylations resulted in two different reaction procedures. Both differ in the way in which the crude product is separated from the catalyst and are referred to as liquid / liquid or vapor processes.

The separation of the crude product and others takes place in liquid / liquid processes

Components, such as the catalyst, by phase separation into a liquid organic and an aqueous phase. Both phases can be withdrawn independently of one another, the crude product, optionally with by-products, being present in the organic phase and the catalyst in the aqueous phase. The advantage of this work-up is that, due to the two-phase configuration, the separation operation can be carried out for a wide range of different product aldehydes, regardless of further properties, such as, for example, the volatility of the product and possibly further by-products. Furthermore, this work-up can be carried out without great thermal stress.

During the second work-up, the steam process, the crude product is separated off in the gas phase. As a function of the boiling point of the olefins used, the steam process can take place in two different forms. The lower aldehydes with a correspondingly low boiling point obtained from easily vaporizable olefins are usually first condensed and removed as a liquid from the remaining, gaseous components, for example unreacted olefin and synthesis gas, separated and then subjected to a thermal separation. Unreacted starting materials are returned in gaseous form to the original or to further post-reactors.

In this respect, one speaks of a gas recirculation or gas cycle process. Higher olefins are mostly reacted by means of a liquid recycle process in which a volume of solution is continuously withdrawn from the reaction zone and fed to a one- or multi-stage evaporation. The resulting separated catalyst solution can then be fed back into the reaction site.

As a function of the olefin starting materials, the equipment structure and the selected

Reaction conditions thus result in a wide range of process-related combination possibilities which require different process parameters and catalyst systems. However, it is common to all procedures that the catalyst used ages over time under the reaction conditions or as a result of the work-up operations. As a result, the yields decrease and / or the achievable isomer ratio shifts unfavorably. It is true that the consequences of aging can be partially compensated for by adjusting the reaction conditions, for example by increasing the temperature in the reaction zone, but ultimately the reaction must be terminated and the used catalyst worked up within regular intervals in order to maintain an economic reaction.

In the patent literature there are some proposals for continuous process management, which should enable high yields over long periods of time.

For example, EP 2 417 093 B1 discloses a process in which the exhaust gas that is obtained in the hydroformylation of unsaturated compounds in the presence of an aqueous catalyst solution containing water-soluble rhodium complex compounds (first reaction stage) is fed to a homogeneous reaction system in which the

Residual amounts of the olefinically unsaturated compounds from the first reaction stage are reacted with organic phosphorus (III) compounds in the presence of complex compounds of rhodium (second reaction stage). The discharge of the second

The reaction stage is first degassed and then passed through two expansion stages with exhaust gas formation. The resulting liquid phase is distilled, the rhodium-containing residue obtained being partly discharged and partly into the second Reaction stage with the addition of fresh rhodium and fresh organic phosphorus (III) compounds is returned. In addition, this step reveals that the activity obtained after the addition of fresh rhodium is lower and this is probably due to catalytically inactive metal.

EP 2 836 474 B1 discloses a process for continuous hydroformylation in which an olefin starting material, which is at least one olefin with 3 to 20

Contains carbon atoms, is reacted at elevated temperature and at elevated pressure in a reaction zone with synthesis gas in the presence of a homogeneous transition metal catalyst complexed with an organophosphorus ligand and free ligand, the catalyst being formed in situ in the reaction zone and the

Adding a solution of a transition metal source to the reaction zone to compensate for catalyst losses, characterized in that the space-time yield of the hydroformylation product in the reaction zone is continuously determined and the rate of addition of the transition metal source into the reaction zone is controlled as a function of the space-time yield, whereby

- Provides an adjusting agent for adjusting the rate of addition of the transition metal source into the reaction zone,

- defines a target value for the space-time yield of the reaction zone of hydroformylation product,

- the actual value for the space-time yield is determined,

- after reaching a lower limit value for the deviation of the actual value from the target value, the amount of transition metal source is determined which is necessary to compensate for the catalyst loss, and

- Adds a solution of the transition metal source to the reaction zone, the rate of addition of the transition metal source in the reaction zone being controlled so that the space-time yield does not exceed an upper limit value for the deviation of the actual value from the target value.

Another possibility for increasing the efficiency of the catalyst system is disclosed in EP 0 246 475 A1. This teaches a process for the production of aldehydes by reacting unsaturated compounds with carbon monoxide and hydrogen

Temperatures from 20 to 150 ° C and pressures from 0.1 to 20 MPa in the liquid phase in Presence of water and a water-soluble, rhodium-containing

Complex compound as a catalyst, the rhodium complex compound, prior to the onset of the hydroformylation reaction, from the rhodium salt of a carboxylic acid having 2 to 18 carbon atoms dissolved in an aliphatic, cycloaliphatic or aromatic hydrocarbon by reaction with carbon monoxide and hydrogen at pressures of 0.1 to 1.8 MPa and Temperatures of 50 to 100 ° C is preformed, the preforming being carried out in the presence of that aqueous solution of a water-soluble triarylphosphine or this aqueous solution being added to the previously prepared rhodium complex compound after the preforming.

So there are a variety of procedures known from the literature in which the

Reaction zone of a homogeneously running one, however configured

Hydroformylation further partial amounts of catalyst, either a worked-up previously removed from the reaction zone, a fresh one or a combination of both

Catalyst types, can be added. For a two-phase process

Hydroformylation, such as, for example, according to the Ruhrchemie- / Rhone-Poulenc process, however, has hitherto not been a suitable procedure for removing and adding a partial amount of catalyst. There is thus great interest in continuous, large-scale process management for hydroformylations which are capable of delivering consistently high selectivities and high product yields over long periods of time.

It is therefore the object of the present invention to provide an improved continuous hydroformylation process which at least partially counteracts the disadvantages of the prior art.

A method according to claim 1 is therefore proposed to solve this problem.

Preferred embodiments of the method according to the invention are in

Subclaims reproduced.

According to the invention, the object is achieved by a continuous two-phase

Carbon monoxide, hydrogen and a transition metal catalyst in a reaction zone, the transition metal being in the form of a water-soluble catalyst complex, the process comprising the following steps one or more times: a) Hydroformylation by reacting the olefins, carbon monoxide and hydrogen on a water-soluble transition metal catalyst comprising water-soluble ones

Organophosphorus ligands in the reaction zone;

c) adding a solvent, a transition metal source and water soluble

Surprisingly, it has been shown that continuous hydroformylations according to the Ruhrchemie- / Rhone-Poulenc process can be carried out virtually indefinitely by means of the process steps specified above, without the need to end the entire process due to the aging of the catalyst and to remove the catalyst in its entirety To withdraw reaction zone and have to work up. With very little intervention in the hydrofromylation process as such, high productivities and high selectivities can be achieved over long periods of time, the overall process advantageously also being able to be run with less catalyst and ligand use compared to the standard processes from the prior art. It is possible to obtain active catalysts with high efficiency directly in the reaction zone. The catalytically active complexes formed from metal and ligand are in the

Equilibrium that can be shifted to more active and selective complexes depending on the chemical environment and the physical boundary conditions. In this respect takes place for the central atom of the catalyst complexes under the

Reaction conditions of the reaction zone usually involve an exchange of the ligands in the ligand sphere. The coordination of the potential ligands at the metal center determines the catalytic activity and in particular the induced regioselectivity and thus ultimately the obtainable isomer ratio in the crude product. The formation of the complexes is influenced not only by the ligands used to build up the desired catalyst, ie hydrogen, carbon monoxide, olefin and organophosphorus ligand, but also by other degradation and by-products present in the reaction zone, which become undesirable due to their incorporation into the ligand sphere of the metal complexes

Properties and can contribute to a deterioration in the synthesis performance. In this respect, it was not foreseeable that a conversion into a highly efficient catalyst would be successful in such an environment of the reaction zone. Without being bound by theory, the fact that a highly efficient catalyst is obtained is attributed to a synergistic interaction of at least two causes. On the one hand, the addition of new catalyst metal takes place in the absence of the olefin in the reaction zone and, on the other hand, the catalyst solution in the reaction zone, diluted by the degradation and by-products, appears to be conducive to the formation of very selective and efficient catalyst complexes. This theory is supported by the fact that supplements of the catalyst metal in the presence of the olefin and to an undiluted solution do not lead to any appreciable increase in the activity and no improvement in the n / i selectivity. Usually only further hydroformylation processes are used to extend the service life of the catalyst in the continuous hydroformylation processes under consideration

Organophosphorus ligands supplied, which in the context of an equilibrium reaction displace the catalyst poisons present in the metal complexes, such as ligand degradation products, and are intended to convert the catalyst back into a more active form. The latter maintenance measures, however, require high amounts of ligand and ultimately cannot prevent the continuous reaction from being terminated and the entire catalyst being exchanged, since the decomposition of the ligands present continuously increases the concentration of the catalyst poisons. Also through

Catalysts recycled to the reaction zone seem, despite the additional addition of fresh catalyst metal, probably based on a different chemical environment and / or due to the different volume flows, not suitable for the formation of similarly efficient catalyst complexes.

The method according to the invention relates to a continuous two-phase

Hydroformylation process. In the method according to the invention are the active Catalyst metal in an aqueous and the organic aldehydes formed, together with any organic by-products formed, in an organic phase formed from them. The olefins are converted in a two-phase system comprising an organic and an aqueous phase. The active metal complex is in turn homogeneously dissolved in the aqueous phase. The process is a continuous process since, in order to carry out the actual reaction, the starting materials are continuously fed into the reaction zone and the products formed are continuously removed therefrom.

By means of the process according to the invention, aldehydes are prepared from olefins.

The implementation can be illustrated using the implementation of propene as an example:

metal

Ligand O

Propene n-butyraldehyde / so-butyraldehyde

Both the straight-chain n- and the branched i-aldehyde are obtained from the hydroformylation. The olefins which can be used can be linear or branched and have a terminal or internal double bond. Examples of such olefins are: ethylene, propylene, 1-butene, 2-butene, 1-pentene, 2-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, 4,4-dimethyl-1- nones, 1-dodecene. Linear olefins with 2 to 8 carbon atoms such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene or mixtures of at least two possible double bond isomers thereof can preferably be used.

The reaction or the reaction of the olefins takes place in the presence of

Carbon monoxide and hydrogen. These starting materials are usually used

together as synthesis gas. The total pressure of hydrogen and carbon monoxide can be 1-200 bar (100-2 * 10 ⁴ kPa), preferably 10 to 100 bar (1 * 10 ³ to 1 * 10 ⁴ kPa). The composition of the synthesis gas, ie the ratio of

Carbon monoxide to hydrogen can be varied within wide limits. In general, synthesis gas is used in which the volume ratio of carbon monoxide is added

Hydrogen is 1: 1 or deviates only slightly from this value. A transition metal catalyst is used for the reaction, the

Transition metal catalyst is in the form of a water-soluble catalyst complex. Transition metals that can be used are, for example, the transition metals of the 8th-10th grade.

Subgroups such as cobalt, rhodium, iridium, iron, ruthenium, osmium and platinum. Cobalt or rhodium can preferably be used, particularly preferably rhodium. The conversion and catalysis takes place in the aqueous phase and requires the metal complexes to be water-soluble. It is usually assumed that the catalyst in the aqueous phase is coordinated both with the starting materials as ligands and with the water-soluble organophosphorus ligands, the latter in particular contributing to the water solubility of the complex. In the course of the hydroformylation and as a function of the chemical environment, however, the ligand sphere can change, for example through the uptake of hydrogen, olefin or carbon monoxide, so that it is assumed that catalyst complexes with mixed and different ligand spheres can be present, which complexes are ultimately still water-soluble.

The method according to the invention can comprise the claimed steps one or more times. The process can preferably be carried out more frequently in order to extend the catalyst service life and thus the overall process time. For example, it is possible to carry out the process as a function of the current synthesis output, the measured isomer ratio or as a function of the salt load of the aqueous catalyst solution. The method can be carried out, for example, 1-100 times, preferably 1-50 times, furthermore preferably 1-10 times. In particular, the invention does not provide for the process to be carried out continuously, i.e. continuously in the context of a hydroformylation. This means that carrying out a pure cycle process with continuous separation and / or processing of the catalyst is not to be included in the process of the invention.

In process step a), hydroformylation takes place by reacting the olefins with carbon monoxide and hydrogen over a water-soluble transition metal catalyst having water-soluble organophosphorus ligands in the reaction zone. In this process step, the starting olefins are catalytically converted into the desired aldehydes. The reaction usually takes place in a reactor into which the starting materials are fed in in gaseous form. The catalyst is located inside the reactor liquid, aqueous phase, through which the gaseous starting materials flow and are saturated. According to the invention, this location in the reactor forms the reaction zone.

Under the term water-soluble organophosphorus ligands, for example

Compounds from the class of the triarylphosphines and the diphosphines are understood which are soluble in water due to the presence of one or more sulfonate or carboxylate groups in the molecule. The water-soluble triaryl, in particular

Triphenylphosphines follow the general formula (I),

where Ar ¹ , Ar ² , Ar ^{3 are} each independently a phenyl or naphthyl group, Y ¹ ,

Y ² , Y ³ each independently represent a straight-chain or branched alkyl group with 1 to 8 carbon atoms, a straight-chain or branched alkoxy group with 1 to 8 carbon atoms, a halogen atom, an OH, CN, NO2 or NR ¹ R ² group in which R ¹ and R ² each represent a straight-chain or branched alkyl group with 1 to 8 carbon atoms, X ¹ , X ² , X ³ independently of one another represent a carboxylate (COO--) and / or a sulfonate - (- S0 ₃ ) radical, mi, rri2, rrb are identical or different numbers from 0 to 3, where at least one number mi, rri2, rri3 is equal to or greater than 1, and, n2, n3 are the same or are different integers from 0 to 5. The negative charge of X ¹ , X ² , X ³ is neutralized by counter ions, for example alkali metal ions, alkaline earth metal or zinc ions, ammonium or quaternary ammonium ions. Preference is given to water-soluble triarylphosphines of the general formula described above in which Ar is each a phenyl radical and X is each a sulfonate radical or a carboxylate radical. Examples of this class of compounds of the general formula given above are triphenylphosphine trisodium trisulfonate (TPPTS), tri-phenylphosphine tri (tetraalkylammonium) trisulfonate, triphenylphosphine tri-sodium tricarboxylate. The sulfonated or carboxylated ones

Arylphosphines can be used as pure compounds. But it can also Mixtures of phosphines are used, which carry different numbers of sulfonate or carboxylate groups. Triphenylphosphine tri-sodium trisulfonate according to the formula (II) can be used particularly preferably as the water-soluble organophosphorus complex ligand:

Sulfonated diphosphines of the general formulas (III) and (IV) are also suitable as water-soluble diphosphines

In (III) each n4 and ns independently of one another stands for 0 or 1, it being possible for the compound of the formula (III) to contain up to six -SChM groups.

In (IV) each hb, m, ns and ng independently of one another stands for 0 or 1, the compound of the formula (IV) containing four to eight -SChM groups.

In the formulas (III) and (IV), M stands for ammonium, a monovalent metal or the equivalent of a polyvalent metal, in particular for sodium, potassium, calcium or barium.

In process step b), the concentration of the olefins in the reaction zone is reduced by reducing the olefin feed to the reaction zone and at least part of the catalyst solution is removed from the reaction system, the partial steps of

Catalyst solution removal and the reduction in the olefin concentration can take place in this or the reverse order, simultaneously or in succession. The

The concentration of the olefins can be achieved, for example, by stopping the feed and allowing the compounds still in the reactor to react.

The molar concentration of the olefins in this step is expediently brought to 10%, preferably 5%, preferably less than 1%, based on the olefin concentration prevailing in process step a). A partial amount of catalyst solution comprises a significant proportion of catalyst solution, which is greater than that part which is removed from the reaction zone, for example in the context of continuous circulation processes. The partial amount can have a volume of more than 5%, preferably more than 10%, preferably more than 15% and furthermore preferably more than 20% of the total aqueous Include catalyst solution. This process step can be initiated, for example, by removing the catalyst solution. Then the

Olefin concentration can be reduced. However, the catalyst solution can preferably only be drained off after the olefin concentration has been reduced.

The reaction system is formed from the reaction zone in the reactor and any further devices present, such as the circulating catalyst stream. The catalyst does not necessarily have to be withdrawn directly from the reaction site. It is possible for the catalyst to be circulated and the catalyst to be removed at another point in the circuit. This measure inevitably also leads to a reduction in the amount of catalyst in the reaction zone.

In process step c), a solvent, a transition metal source and water-soluble organophosphorus ligands are fed to the reaction system, and the components can be fed in simultaneously or in any order. The volume of catalyst removed can therefore be partially, completely or in excess replaced by a solvent, for example water. To the now diluted

The transition metal source and then the water-soluble organophosphorus ligand can then be added to the catalyst solution in the reaction zone. The latter additions can be made, for example, in the form of concentrated aqueous solutions with some of the solvent. However, it is also possible to supply all components, solvents, transition metal source and complex ligand to the reaction system as a solution. The components can be brought together in the reaction zone or else in the reaction system. Furthermore, it is also possible to supply the complex ligands, at least in part, as part of the transition metal source. This means that, for example, a preformed catalyst complex with

water-soluble organophosphorus complex ligands can be used as transition metal source. Possible non-preformed, water-soluble transition metal sources are, for example, rhodium sources such as [Rh (octanoate) 2] 2, [Rh (acac) (CO) 2], [Rh (2-ethylhexanoate) 3], [Rh (2-ethylhexanoate) 2] 2, [Rh (acac) (cod)], [Rh (cod) CI] 2, [Rh (acac) 3],

[Rh (cod) ₂ ] BF ₄ , [Rh (OAc) ₃ ] or mixtures thereof. After the components have been added, the new catalyst solution can be preformed under synthesis gas for a certain period of time, the transition metal source being under the chemical and applied conditions physical conditions and in the presence of the corresponding water-soluble organophosphorus ligands is converted into the active catalyst.

In process step d), the concentration of the olefins in the reaction zone is then increased by increasing the olefin feed to the reaction zone and hydroformylation by reacting the olefins with carbon monoxide and hydrogen. The olefin concentration in the reaction zone can be increased by starting the feed of the gaseous olefin. The olefin concentration can expediently be increased to the value that was present in process step a). However, it is also possible to feed in a higher olefin concentration due to the increased catalyst activity. As the olefin is fed back into the reaction zone, metal-catalyzed aldehydes are then formed again by means of the synthesis gas.

In a preferred embodiment of the process, in process step b) the partial step of reducing the olefin concentration before the partial withdrawal of the

Catalyst solution take place. It has been found to be particularly advantageous for the interruption times in the hydroformylation that the reduction in the olefin concentration takes place before the partial removal of the catalyst solution. Since in this variant a larger

If the catalyst concentration is present, the olefin concentration can be reduced more quickly compared to an embodiment in which part of the catalyst solution has already been removed. In this embodiment, less olefin is advantageously discharged with the partial amount of catalyst.

In a preferred embodiment of the process, in process step b) the molar olefin concentration in the reaction zone can be greater than or equal to 50% and less than or equal to 100% based on the olefin concentration in the reaction zone

Process step a) can be reduced. In order to obtain the most active catalyst possible after partial substitution of the catalyst solution, it has been found to be particularly advantageous that the olefin content in the reaction zone is significantly reduced. The substitution can particularly preferably take place entirely in the absence of olefins in the reaction zone. This can lead to particularly active and selective catalysts in the reaction zone after the substitution, which improves the economy of the entire process. GC methods can be used to determine the olefin concentration still present in the reaction zone. Within a preferred aspect of the process, in process step b) a volume of greater than or equal to 10% and less than or equal to 50% of aqueous

Catalyst solution can be taken out of the reaction system. In order to obtain the most economical method possible, the partial withdrawal amounts given above have proven to be particularly suitable. Smaller amounts withdrawn can lead to insufficient restoration of the catalyst activity and higher amounts withdrawn to an excessive disruption of the equilibrium in the reaction zone. The partial withdrawal volume can also preferably be> 15% and <45%, further preferably> 20% and <40%.

In a further embodiment of the process, the volume of liquid components supplied in process step c) can be greater than or equal to 20% and less than or equal to 200% based on the catalyst solution withdrawn in process step b). In order to obtain a very active, reactivated catalyst solution with a relatively low proportion of disruptive catalyst poisons, it has been found to be particularly suitable that the volume of the partial withdrawal amount removed from the reaction zone is approximately compensated for by the volume of the newly added components. A further dilution by adding a larger volume, as indicated above, is usually harmless within the stated limits and can contribute to a further reduction in the salt content or the organic components in the aqueous catalyst solution. These added amounts can also be other setting components with which one can react to the increased efficiency of the catalyst solution. Smaller volumes can be disadvantageous since this can lead to insufficient dilution of the total catalyst phase in the reaction zone.

In a further embodiment of the process, in process step c), as transition metal source, rhodium compounds selected from the group of rhodium (III) salts such as Rh-2-ethylhexanoate, acetate, oxalate, propionate, malonate, Rh (NOs ) 3,

Rh (S0 ₄ ) ₃ , RhCh or the rhodium complex compounds such as

Cyclopentadienylrhodium compounds, [RhCl (Cyclooctadiene-1,5)] ₂ , rhodium acetylacetonate, the rhodium carbonyl compounds such as Rh3 (CO) i2, Rh ₆ (CO) i ₆ or in the form of

various rhodium oxides or mixtures of at least two compounds thereof are added. This group of Rh compounds has proven to be particularly suitable Exposed rhodium source. These compounds can be converted rapidly into the desired active catalyst species under the physical and chemical conditions of the reaction system or the reaction zone and deliver after a short period of time

Preformation times high productivity and selectivity. This can contribute to increasing the economy and the service life of the process. In particular, the use of these rhodium sources can save additional structures for preforming the catalyst, since the formation of the catalyst, i.e. the conversion into the active catalyst with hydrogen, carbon monoxide and water-soluble organophosphorus complex ligands, takes place in the reaction zone itself.

As part of a further, preferred aspect of the method, in

Process step c) with preformed rhodium complexes as transition metal source

Organophosphorus ligands are added to the reaction system. It has proven to be advantageous to shorten the preformation time of the catalyst in the reaction zone

pointed out that already preformed catalysts are fed to the reaction zone as a rhodium source. In this, equilibrium is established more quickly and adaptation to the reaction conditions takes place. This can be very short

Interruptions in the synthesis to substitute the catalyst solution can be guaranteed.

Within a further embodiment of the process, organophosphorus ligands can be used in process step c) in a molar ratio of greater than or equal to 20 and less than or equal to 400 based on the amount removed in process step b)

Transition metal amount are added. The addition of the abovementioned ligands has been found to be particularly suitable for the rapid establishment of the most active possible catalyst assembly in the reaction zone. This amount can contribute to a particularly rapid preformation of the rhodium-phosphine complexes newly formed by the addition of organophosphorus ligands and, moreover, to a reactivation of the catalysts remaining in the reaction zone. The latter were possibly through

Catalyst poisons impaired in their synthesis performance and / or selectivity. Higher ratios can lead to an excessively high organic / salt loading of the aqueous phase and lower ratios to inadequate reactivation of the catalyst metal centers. Within a preferred embodiment of the process, a solution of a rhodium compound comprising organophosphorus ligands can be used in process step c)

Reaction system are supplied. Simultaneous addition of a non-preformed solution of a rhodium compound, which also has water-soluble organophosphorus ligands, has been found to be particularly suitable to simplify the addition steps and to quickly establish equilibrium. This procedure eliminates the need for additional technical structures in order to preform the catalyst. Furthermore, the preforming in the reaction zone can take place more quickly than if the components were added separately. The addition can preferably also take place directly to the reaction zone.

In a preferred aspect of the process, organophosphorus ligands can be fed to the reaction system in process step c) before the transition metal source is fed in. The catalyst solution should already be at a high level

Signs of aging, such as an unfavorably changed / worsened isomer ratio or only very inadequate activity, it can turn out to be beneficial that the residual amount of catalyst solution remaining in the reaction zone is brought into contact with a water-soluble organophosphorus ligand before the transition metal source is added, before the fresh transition metal source is added. This procedure can contribute to a more selective activation of the remaining catalyst and, in comparison with a simultaneous addition of a transition metal source and organophosphorus ligands, a more active and more selective catalyst is obtained in the reaction zone. The addition of the

Organophosphorus ligands can take place directly in the reaction zone or, for example, via addition to the catalyst circuit in the reaction system.

According to a further, preferred embodiment of the method, im

Process step c) first a portion of the solvent, then the transition metal source dissolved in a solvent and then the organophosphorus ligands

Reaction system are supplied. For a controlled conduct of the reaction it has been found to be particularly suitable for the addition in this process step to take place in the order given above. As a result of the sequential addition, a dilute aqueous catalyst solution can always first be obtained in the reaction zone, to which then the other components are added. The establishment of equilibrium can also be accelerated by suitable technical measures or by the synthesis gas convection of the solution in the reaction zone.

According to a preferred characteristic of the method, the total concentration of organic ligands and salts present in the aqueous solution of the reaction zone by method steps b) and c) can be greater than or equal to 10% and less than or equal to 50% compared to the concentration of the organic ligands and the Salts in the aqueous solution of the reaction zone are reduced at the end of process step a). Surprisingly, it has been found that the process according to the invention is able to significantly reduce the salt content and / or the organic load in the aqueous catalyst solution of the reaction zone. In particular, the concentration of the ligand degradation products can be reduced, as a result of which the longevity of the catalyst in the reaction zone is increased overall. The amount of organophosphorus ligands in the aqueous solution can be determined, for example, via HPLC measurements.

In particular, the proportion of TPPTS degradation products can be reduced, which leads to an improvement in the isomer ratio. The organic ligands include in particular complexing agents with a carbon skeleton and heteroatoms, the complex formation taking place via the heteroatoms. The organic ligands thus include the desired, functional organophosphorus ligands and their degradation products.

In addition, the group of organic ligands also includes the ligands of the water-soluble, added transition metal sources, for example in the form of acetate or similar compounds with carbon and heteroatom content.

Within a further embodiment of the process, in process step c) the pH in the aqueous solution of the reaction zone can be adjusted to a range of greater than or equal to pH 4 and less than or equal to pH 10 after adding the components. In order to obtain the highest possible catalyst activity, it has also proven helpful to check the pH of the catalyst solution in the after the addition sequence

Set reaction zone. This can be done using known adjusting agents such as inorganic acids or bases. It is also possible to provide the newly added amount of catalyst with this already and thus to achieve an acceleration of the process / reactivation times. In a further preferred embodiment, the pH can be greater than or equal to or equal to pH 5 and less than or equal to pH 8, furthermore preferably between greater than or equal to pH 5.5 and less than or equal to pH 7.

In a further embodiment of the method, the molar ratio of

added organophosphorus ligands to added transition metal in the

Method step c) be greater than or equal to 20 and less than or equal to 500. To

Stabilization of the transition metal source and to accelerate the equilibrium setting, it has been found to be beneficial that the water-soluble

Organophosphorus ligand is used in a large excess in this step.

Furthermore, preferred ratios are between greater than or equal to 120 and less than or equal to 450 and preferably greater than or equal to 150 and less than or equal to 400.

According to a further preferred embodiment of the method, the

Process steps b) and c) the concentration of the inorganic cations in the solution of the reaction zone can be reduced by greater than or equal to 5%. It has also been found to be very advantageous that, in addition to the concentration of organic ligands in the reaction zone, the amount of inorganic cations is also reduced. The inorganic cations include, for example, alkali and alkaline earth ions. Without being bound by theory, these ions can apparently either be part of the

Be catalyst complexes or contribute to an improvement in the solubility of the olefins in the aqueous phase by changing the distribution equilibrium of the olefin between the aqueous and organic phases. By reducing the concentration of the cations, the polarity of the aqueous phase is reduced and a more advantageous phase equilibrium can be achieved for the olefin. The latter can in particular contribute to an increase in the reaction rate. In particularly preferred embodiments, the concentration of the inorganic cations in the solution of the reaction zone can be reduced by greater than or equal to 10%, particularly preferably by greater than or equal to 15%. These areas of reduction of the cations can contribute to a particularly efficient restoration of the catalyst activity. The

The concentrations can be measured using ICP methods, for example.

Further details, features and advantages of the subject matter of the invention emerge from the subclaims and from the following description of the figures and the associated examples. It shows the: 1 schematically shows the implementation of a continuous Ruhrchemie- / Rhone-Poulenc hydroformylation process;

2 schematically shows the process sequence when carrying out the hydroformylation process according to the invention.

FIG. 1 shows schematically the implementation of a continuous Ruhrchemie- / Rhone-Poulenc hydroformylation process. The olefin starting material and synthesis gas are fed continuously to an aqueous, active catalyst solution in a reaction zone. The reaction conditions used lead to a chemical degradation of the catalyst, as a result of which the synthesis performance and the selectivity of the conversion deteriorate. In response to the deterioration, additional ligand, a water-soluble organophosphorus complex ligand such as TPPTS, is added to the reaction zone at intervals. Due to the equilibrium reaction with the newly added ligand and with partial displacement of the catalyst poisons from the metal complexes, both the synthesis performance and that improve

Isomer ratio. The hydroformylation is then continued as usual with the addition of synthesis gas and olefin. After multiple additions of the water-soluble organophosphorus complex ligand, the salt and organic load is in the

Catalyst solution, however, so high that the reaction ends and the entire

Catalyst solution must be worked up.

FIG. 2 schematically shows the process sequence of the process according to the invention. After a certain duration of the hydroformylation, as in the prior art process, there is a partial deactivation of the metal catalysts, which is noticeable by a poorer yield and / or a poorer isomer ratio. In this case, a portion of the catalyst solution is discharged from the reaction site or the reaction system. The ejected portion is through

Replaces solvent and a dilute catalyst solution is obtained. In addition, at the same time, before or after the discharge, the amount of olefin at the reaction site is reduced. The latter can be achieved, for example, by stopping the supply of olefins and reacting to completion of the olefin still present in the reaction zone. To the Olefin-depleted reaction zone are now simultaneously or successively one

Rhodium source, and other water-soluble organophosphorus complex ligands supplied. This supplemented catalyst solution is in the absence of olefins and

Presence of synthesis gas preformed to the active catalysts. After

Preformation, the olefin feed is restarted and the hydroformylation takes place with a significantly better synthesis performance and an improved isomer ratio. In this way, the continuous hydroformylation reaction can be continued consistently over a significantly longer period of time compared with the prior art processes.

Examples

The advantages of the process according to the invention are demonstrated by the following examples.

Example 1 (not according to the invention, addition takes place in the presence of olefin)

A used aqueous catalyst solution (Rh with TPPTS as organophosphorus ligands and a ligand ratio P (III): Rh of approx. 90: 1) was used in a semi-continuous apparatus and at 50 bar synthesis gas pressure, 137 ° C, pH 6.0 and a propylene - Use of 60 g / h operated over 14 h. One gets as a measure for the

Productivity of the catalyst has a p-value of 0.272 (kg _Aidehyd / L _Katisg xh) than

Starting level. Then, in two steps, 20% and 35% of the

Catalyst solution removed and replaced with the appropriate amount of deionized water. Although the amount of rhodium at the reaction site by these two

Partial discharges was almost halved, the p-value only decreased by approx. 20%. However, as a result of the dilution of the catalyst solution, the regioselectivity with respect to the n-aldehyde fell from 91% to 89%. The original amount of rhodium in the reactor was then restored by adding rhodium (III) acetate during the ongoing hydroformylation, that is, with the addition of synthesis gas and feed olefin. The addition of rhodium (III) acetate resulted in a lowering of the P (III): Rh ratio (219 vs. 112 ppm or 74: 1 vs. 43: 1), the lowering of the ligand ratio having no effect on the

Productivity still showed selectivity. Actually, it should be a clear one

Increase in activity by adding more rhodium. Furthermore, the regioselectivity should decrease further due to the lower P (III): Rh ratio. The following values were obtained for the experiment:

Table 1: Example 1 - withdrawal and addition under standard conditions, especially in the presence of olefin. 50 bar, 60 g / h propylene input, pH 6.0, n-C4-al is calculated as nl (n + i)

The above table makes it clear that the supplementation of the rhodium removed, without returning the olefin concentration in the reaction zone, only leads to one

insufficient recovery of the synthesis output and no improvement in the n: i isomer ratio. These values also do not improve as a function of time, so that this effect cannot be attributed to kinetic effects, such as, for example, insufficient time for the formation of the actual active catalyst species. Presumably the metal introduced as rhodium (III) acetate could be among the

Reaction conditions are not converted into the catalytically active rhodium (I) complex at all or only to an insufficient extent. However, there may also be increased deactivation of the newly added rhodium due to undesired and competing complex formation with coordinating ligand degradation products. Under

Under certain circumstances, the added rhodium (III) could form stable rhodium (III) -alkenyl complexes with the olefins present in the reaction zone, which hydroformylation are inactive and cannot be converted into catalytically active rhodium (I) complexes under the conditions in the reaction zone.

Example 2 (process according to the invention, supplement in the absence of olefins)

At 126 ° C., 50 bar, with a propylene input of 60 g / h and a pH of 6.0, the basic _{output of the catalyst solution} used was p = _0.155 (kg _aidehyde / _atisg. Xh) over about 23 h. and 90.9% n-aldehyde content determined. Subsequently, 21% of the catalyst solution was removed and the loss in volume was compensated for with water. The p-value fell to _0.138 (kg _aidehyde / _atisg. Xh) and the n-aldehyde content to 90.0%. After 36 h, the system was let down to 10 bar and then a pressure of 50 bar was set with synthesis gas, the propylene present in the reactor being removed. Rhodium (III) acetate was added in accordance with the amount of catalyst removed beforehand and the catalyst solution was stirred at 50 bar synthesis gas pressure and 121 ° C. for 3 h. The propylene addition was then restarted. After this procedure, a significantly increased p-value of _0.169 (kg _Aidehyd / _atisg. Xh) was obtained. This value for the synthesis output is above that of the initial level and is high for a used and refreshed catalyst at 126 ° C. The p-value allows a statement about the amount of product achieved per

Catalyst volume and time. The selectivity fell to 89.8% n-aldehyde, however. After 48 h, the ligand TPPTS was added to the system in order to increase the P (III): Rh to a ratio of> 90: 1. The volume introduced by the TPPTS was strong

Dilution of the catalyst circuit and correspondingly the rhodium concentration resulted, which led to a decrease from p-value to p = _0.130 (kg _Aidehyd / o _daily xh).

However, if the dilution is taken into account, a significantly more active catalyst results in comparison with Example 1. The selectivity also increased to n-proportion of 90.7%. The absence of propylene during the addition seems to be decisive for an effective rhodium (III) addition, since, in contrast to Example 1, higher productivity and an improved isomer ratio are established after the addition. In addition, the temperature can be lowered again after supplementation, which can increase the catalyst service life again in the further course of the process.

Table 2: Example 2 - removal and addition under modified conditions; 50 bar, 60 g / h propylene input, pH 6.0, n-C4-al is calculated as nl (n + i)

Example 3 (according to the invention)

The procedure described in Example 2 was repeated four times in a further experiment at 50 bar, 126 ° C., 140 g / h propylene input and pH 6. The new catalyst solution was always added in the absence of starting olefin. The basic hydroformylation level was determined to be p = 0.166 (kg _Aidehyd / _atisg. Xh) and 92.5% n-C4-al. The activity of the catalyst solution exceeded after the supplementation of the removed

Catalyst volume the base level and increased on average to p = 0.178

(kg _aidehyde / _atisg. xh). The regioselectivity decreased after the 3rd sequence down to 90.6% n-content for P (III): Rh from 60: 1 and was increased in the 4th sequence by further addition of ligands to a ratio of 80: 1, which is a Selectivity of 91.1% gave.

Table 3.1: Withdrawal and addition under fully continuous conditions, preforming in the reactor 3 h, 50 bar, 140 g / h propylene input, pH 6.0, n-C4-al is calculated as nl (n + i)

Since the partial substitution aims to increase the activity of the catalyst solution used by discharging deactivating components, the concentrations of corresponding decomposition products were also monitored (Table 3.2). Before the first Withdrawal from the catalyst, the concentrations of TPPOTS were 4.4% and one of the ligand degradation products (K5) was 7.9%. The decomposition products therefore include all those organic compounds in the reaction solution which have at least part of the basic structure of the organic ligand used and have been chemically modified, at least in part, via the chemical conditions prevailing in the reaction zone. The chemical modifications of the ligands used can include, for example, one or more oxidation / reduction processes and splitting off of one or more functional or CH groups. The total salt content of the catalyst solution, measured by HPLC analysis, was 29.1%. After the first substitution sequence including the rhodium and TPPTS addition, the concentrations of TPPOTS were 3.5% and of K5 6.1%. The total salt content was 23.2% and therefore significantly lower than at the initial level. The TPPTS content was 9.8% as a result of the supplement compared to 11.8% previously.

Table 3.2 \ Example 3 - Change in the salt content after partial catalyst substitutions.

Overall, the salt concentrations could be reduced by> 20% in the first substitution. The TPPTS content, on the other hand, was kept relatively stable by the additives. For the data it should be noted that the P (III) decomposition was not compensated for during the first substitution sequences. Only in the last sequence was a clear excess of TPPTS added so that the TPPTS content was brought to 12.5% or a P (11): Rh ratio of> 80: 1. Example 4 (combination of the individual metal sources and addition of ligands) In this experiment, at 139 ° C, 50 bar, a propylene input of 145 g / h and a pH of 6.0 over 427 h, the decrease in activity and selectivity of a catalyst solution was followed which had a very low P (l II): Rh ratio of <50: 1. The p-value sank steadily within the reaction time from 0.237 (kgAidehyd / atisg.xh) to 0.123 (kgAidehyd / atisg.xh). The substitution of 20% of the catalyst volume was then initiated. The

Propylene feed was stopped, the propylene in the reactor was converted and 20% of the catalyst volume was withdrawn from the catalyst circuit. The missing

The catalyst volume was replaced directly with a corresponding amount of rhodium (III) acetate dissolved in an aqueous TPPTS solution (approx. 30% by weight; resulting in P (III): Rh = 102: 1). At the reaction temperature (138 ° C) and under a synthesis gas atmosphere (50 bar), the approximately propylene-free reaction mixture was stirred for 3 h before the

Propylene feed started slowly and increased up to 145 g / h. In the first 20 h after replacement, the p-value increased from _0.123 (kg _Aidehyd / _atisg. Xh) to 0.184

(kgAidehyd / atisg.x h) and in the following 24 h further to 0.209 (kgAidehyd / Uatisg.x h). Since the substitution was carried out here in one step, i.e. by simultaneous addition of the rhodium source in a solution with or with simultaneous addition of ligands, it was also possible to dispense with prior stabilization of the catalyst solution by TPPTS. The results of this sequence are as follows:

Table 4: Substitution on an inactive catalyst solution (fully continuous). 50 bar, 145 g / h propylene input, pH 6.0, n-C4-al is calculated as nl (n + i)

Example 5 (aged catalyst solution)

In a preferred variant of the method, an attempt was made to carry out the substitution sequence on a very severely aged catalyst solution. At 50 bar, 138 ° C., 140 g / h of propylene and a pH of 6.0, the basic level of the reaction was determined and the substitution sequence began with the removal and dilution. The hydroformylation collapsed and the experiment had to be terminated. It was not possible to reactivate the catalyst.

Table 5: Example 5 - Substitution on an inactive catalyst solution (fully continuous). 50 bar, 140 g / h propylene input, pH 6.0, n-C4-al is calculated as nl (n + i)

If there is already a low ligand-to-rhodium ratio in a very heavily aged catalyst solution, the mere substitution of the metal cannot reactivate the catalyst solution. In these cases the ligands are the determining factor and not the metal. Nevertheless, reactivation can be achieved using the method according to the invention. A possible method for these cases is shown in Example 6.

Example 6 (aged catalyst solution)

Under modified conditions, further ligand was first added to the catalyst solution used in example 5 and the system was thus stabilized (50 bar, 136 ° C., 40 g / h propylene input, pH 6.0). A clear increase in activity and selectivity could be observed just through the addition of ligand, which proves that the ligand concentration is the determining factor for the productivity of the catalyst. After stabilization by addition of ligands, the substitution sequence according to the invention was carried out twice, the preformation time being 3 h in each case. The reduction in temperature from 136 ° C. to 131 ° C. after stabilization and the respective possible increase in the use of olefins after the substitutions (40 g / h-45 g / h-55 g / h) are signs of a significant increase in catalyst activity. The result shows that very inactive catalyst solutions can also be subjected to substitution and reactivation. To do this, however, these special catalyst solutions must first be stabilized by adding more ligands. The results of the substitution are shown in Table 6.

Table 6: Example 6 - substitution on an inactive catalyst solution after previous stabilization (fully continuous), n-C4- al is calculated as nl (n + i)

Claims

1. Continuous two-phase hydroformylation process for the preparation of aldehydes from olefins using carbon monoxide, hydrogen and a

Transition metal catalyst in a reaction zone, the transition metal being in the form of a water-soluble catalyst complex, thereby

characterized in that the method comprises the following steps one or more times:

a) hydroformylation by reacting the olefins, carbon monoxide and hydrogen on a water-soluble transition metal catalyst having water-soluble organophosphorus ligands in a reaction zone;

b) reducing the concentration of olefins in the reaction zone

Reducing the olefin feed to the reaction zone and removing at least part of the catalyst solution from the reaction system, wherein the partial steps of removing the catalyst solution and reducing the olefin concentration can take place in this or the reverse order, simultaneously or one after the other;

c) supplying a solvent, a transition metal source and water-soluble organophosphorus ligands to the reaction system, it being possible for the components to be supplied simultaneously or one after the other in any order;

2. The method according to claim 1, wherein in process step b) the substep of

Reduction of the olefin concentration takes place before the partial withdrawal of the catalyst solution.

3. The method according to any one of the preceding claims, wherein in process step b) the molar olefin concentration in the reaction zone is greater than or equal to 50% and less than or equal to 100% based on the olefin concentration in the reaction zone in process step a) is reduced.

4. The method according to any one of the preceding claims, wherein in process step b) a volume of greater than or equal to 10% and less than or equal to 50% of aqueous catalyst solution is removed from the reaction system.

5. The method according to any one of the preceding claims, wherein the im

Process step c) supplied volume of liquid components is greater than or equal to 20% and less than or equal to 200% based on the catalyst solution removed in process step b).

6. The method according to any one of the preceding claims, wherein in process step c) as transition metal source rhodium compounds selected from the group of rhodium (III) salts such as Rh-2-ethylhexanoate, acetate, oxalate, propionate, malonate, Rh (NC> 3) 3, Rh (SC> 4) 3, RhCh or the rhodium complex compounds such as cyclopentadienylrhodium compounds, [RhCI (cyclooctadiene-1, 5)] ₂ ,

Rhodium acetylacetonate, to which rhodium carbonyl compounds such as Rh3 (CO) i2, Rh ₆ (CO) i ₆ or in the form of the various rhodium oxides or mixtures of at least two compounds thereof are added

7. The method according to any one of claims 1-5, wherein in process step c) as

Transition metal source with preformed rhodium complexes

Organophosphorus ligands are added to the reaction system.

8. The method according to any one of the preceding claims, wherein in process step c) organophosphorus ligands are added in a molar ratio of greater than or equal to 20 and less than or equal to 400 based on the amount of transition metal removed in process step b).

9. The method according to any one of the preceding claims, wherein in process step c) a solution of a rhodium compound comprising organophosphorus ligands is fed to the reaction system.

10. The method according to any one of claims 1-8, wherein in process step c) before the supply of the transition metal source organophosphorus ligands

Reaction system are supplied.

11. The method according to any one of claims 1-8, wherein in process step c) first a partial amount of the solvent, then that dissolved in a solvent

Transition metal source and then the organophosphorus ligands are fed to the reaction system.

12. The method according to any one of the preceding claims, wherein by the

Process steps b) and c) the total concentration of organic ligands and salts present in the aqueous solution of the reaction zone by greater than or equal to 10% and less than or equal to 50% compared to the concentration of the organic ligands and the salts in the aqueous solution of the reaction zone at the end of process step a) can be reduced.

13. The method according to any one of the preceding claims, wherein in method step c) the pH in the aqueous solution of the reaction zone is adjusted to a range of greater than or equal to pH 4 and less than or equal to pH 10.

14. The method according to any one of the preceding claims, wherein the molar

The ratio of added organophosphorus ligands to added rhodium in process step c) is greater than or equal to 20 and less than or equal to 500.

15. The method according to any one of the preceding claims, wherein by the

Process steps b) and c) the concentration of the inorganic cations in the solution of the reaction zone is reduced by greater than or equal to 5%.